Preparation of complex metal oxides

Abstract

The present invention provides a process for making a complex metal oxide comprising the formula A x B y O z . The process comprises the steps of: (a) reacting in solution at a temperature of between about 75° C. to about 100° C. at least one water-soluble salt of A, at least one water-soluble salt of B and a stoichiometric amount of a carbonate salt or a bicarbonate salt required to form a mole of a carbonate precipitate represented by the formula A x B y (CO 3 ) n , wherein the reacting is conducted in a substantial absence of carbon dioxide to form the carbonate precipitate and wherein the molar amount of carbonate salt or bicarbonate salt is at least three times the stoichiometric amount of carbonate or bicarbonate salt required to form a mole of the carbonate precipitate; and (b) reacting the carbonate precipitate with an oxygen containing fluid under conditions to form the complex metal oxide.

1. A process for making a complex metal oxide comprising the formula
   A x B y O z    
 wherein
 A is at least one metallic element selected from the group consisting of elements of Groups 2, and 3, and the Lanthanide elements of the IUPAC Periodic Table of the Elements, which has an oxidation state ranging from +1 to +3; 
 B is at least one metallic element having an oxidation state ranging from +1 to +7 selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, copper, and nickel; 
 O is an oxygen atom; 
 x is a number from about 1 to about 10; 
 y is a number greater than 0 and equal to or less than about 10 for each element B; and 
 z is a number that renders the complex metal oxide substantially charge neutral, 
 
 the process comprising the steps of: 
 (a) reacting in a solution at a temperature of between about 75° C. to about 100° C. at least one water-soluble salt of A, at least one water-soluble salt of B and a stoichiometric amount of a carbonate salt or bicarbonate salt required to form each mole of a carbonate precipitate represented by the formula
   A x B y (CO 3 ) n    
 wherein n is a number that renders the carbonate precipitate charge neutral, 
 
 
       wherein the reacting is conducted in a substantial absence of carbon dioxide to form the carbonate precipitate and wherein the molar amount of carbonate salt or bicarbonate salt is at least three times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of the carbonate precipitate, and wherein the carbonate salt or bicarbonate salt is selected from the group consisting of NaHCO 3 , KHCO 3 , CsHCO 3 , Na 2 CO 3 , and K 2 CO 3 ; and
 (b) reacting the carbonate precipitate with an oxygen containing gas at a temperature of from between about 650° C. to about 1,200° C. to form the complex metal oxide. 
 
     
     
       2. The process of  claim 1  wherein the complex metal oxide comprises a complex metal oxide selected from the group consisting of Ca 2 Fe 0.5 Mn 1.5 O 5 , Ca 2 Fe 1.5 Mn 0.5 O 5 , Ca 2 Fe 2 O 5 , and Ca 2 Mn 2 O 5 . 
     
     
       3. The process of  claim 1  wherein the complex metal oxide comprises Ca 2 FeMnO 5  and wherein the reacting step (a) comprises reacting Ca(NO 3 ) 2 , MnCl 2 , and Fe(NO 3 ) 3  with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of Ca 2 FeMn(CO 3 ) 5  precipitate; and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5  with air at a temperature of from between about 650° C. to about 950° C. to form the complex metal oxide comprising Ca 2 FeMnO 5 . 
     
     
       4. The process of  claim 1  wherein the complex metal oxide comprises Ca 2 FeMnO 5  and wherein the reacting step (a) comprises reacting Ca(NO 3 ) 2 , Mn(NO 3 ) 2 , and Fe(NO 3 ) 3  with from 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of Ca 2 FeMn(CO 3 ) 5  precipitate; and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5  with air at a temperature of from between about 650° C. to about 950° C. to form the complex metal oxide comprising Ca 2 FeMnO 5 . 
     
     
       5. The process of  claim 1  wherein the carbonate precipitate comprises Ca 2 FeMn(CO 3 ) 5  and wherein the reacting step (a) comprises reacting at least one water-soluble salt of the cations Ca(II), Mn(II), and Fe(II) with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of Ca 2 FeMn(CO 3 ) 5 . 
     
     
       6. The process of  claim 1  wherein the carbonate precipitate comprises Ca 2 FeMn(CO 3 ) 5  and wherein the reacting step (a) comprises reacting water-soluble salts of the cations Ca(II), Mn(II), and Fe(III) with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of Ca 2 FeMn(CO 3 ) 5 . 
     
     
       7. The process of  claim 1  wherein the complex metal oxide comprises one or more of:
 Ca 2 Mn i Fe m O q  where 0≦i≦2 and 0≦m≦2, wherein i+m=2 and 4≦q≦7; 
 Ca 2−x Mg x Mn y Fe z O n  where 0.1<x<0.9; 0≦y ≦2 and 0≦z≦2, wherein y+z=2 and 4≦n≦7; 
 Ca 2 FeMnO 5 ; 
 Ca 2 Fe 2 O 5 ; 
 Ca 2 Co 2 O 5 ; 
 Ca 2 Mn 2 O 5 ; 
 CaMgFeMnO 5 ; and 
 Ca 2−p Ln p Fe z Mn y O n  wherein 0.1<p<0.9, 0≦y≦2 and 0≦z≦2, wherein y+z=2 and 0≦p≦1, Ln is an element from the Lanthanide series of elements and n is a value chosen so as to render the complex metal oxide charge neutral. 
 
     
     
       8. The process of  claim 2  wherein the complex metal oxide comprises Ca 2 Fe 2 O 5 . 
     
     
       9. The process of  claim 8  wherein the reacting step (a) comprises reacting Ca(NO 3 ) 2  and FeCl 2  with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of Ca 2 Fe 2 (CO 3 ) 4  precipitate; and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 Fe 2 (CO 3 ) 4  with air at a temperature of from between about 650° C. to about 850° C. to form the complex metal carbonate comprising Ca 2 Fe 2 O 5 . 
     
     
       10. The process of  claim 8  wherein the reacting step (a) comprises reacting Ca(NO 3 ) 2  and Fe(NO 3 ) 3  with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of Ca 2 Fe 2 (CO 3 ) 4  precipitate; and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 Fe 2 (CO 3 ) 4  with air at a temperature of from between about 650° C. to about 850° C. to form the complex metal oxide comprising Ca 2 Fe 2 O 5 . 
     
     
       11. The process of  claim 1  wherein the complex metal oxide comprises Ca 2 FeMnO 5  and wherein the reacting step (a) comprises reacting Ca(NO 3 ) 2 , MnCl 2 , and Fe(NO 3 ) 3  with from 3 to 10 times the stoichiometric amount of a compound selected from the group consisting of NaHCO 3 , KHCO 3 , CsHCO 3 , Na 2 CO 3 , and K 2 CO 3  for every mole of the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5 : and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5  with air at a temperature of from between about 650° C. to about 950° C. to form the complex metal oxide comprising Ca 2 FeMnO 5 . 
     
     
       12. The process of  claim 2  wherein the complex metal oxide comprises Ca 2 Mn 2 O 5 . 
     
     
       13. The process of  claim 12  wherein the reacting step (a) comprises reacting Ca(NO 3 ) 2  and MnCl 2  with from 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of the carbonate precipitate comprising Ca 2 Mn 2 (CO 3 ) 4 ; and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 Mn 2 (CO 3 ) 4  with air at a temperature of from between about 650° C. to about 850° C. to form the complex metal oxide comprising Ca 2 Mn 2 O 5 . 
     
     
       14. The process of  claim 12  wherein the reacting step (a) comprises reacting Ca(NO 3 ) 2  and Mn(NO 3 ) 2  with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of the carbonate precipitate comprising Ca 2 Mn 2 (CO 3 ) 4 ; and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 Mn 2 (CO 3 ) 4  with air at a temperature of from between about 650° C. to about 850° C. to form the complex metal oxide comprising Ca 2 Mn 2 O 5 . 
     
     
       15. The process of  claim 1  wherein the reacting step (a) comprises reacting at least one water-soluble salt of the cations Ca(II), Mn(II), and Fe(II) with 3 to 10 times the stoichiometric amount of a compound selected from the group consisting of NaHCO 3 , KHCO 3 , CsHCO 3 , Na 2 CO 3 , and K 2 CO 3  for every mole of the carbonate precipitate. 
     
     
       16. The process of  claim 1  wherein the reacting step (a) comprises reacting water-soluble salts of the cations Ca(II), Mn(II), and Fe(III) with 3 to 10 times the stoichiometric amount of a compound selected from the group consisting of NaHCO 3 , KHCO 3 , CsHCO 3 , Na 2 CO 3 , and K 2 CO 3  for every mole of the carbonate precipitate. 
     
     
       17. The process of  claim 1  wherein the complex metal oxide comprises Ca 2 FeMnO 5  and wherein the reacting step (a) comprises reacting molar quantities of Ca(NO 3 ) 2 , MnCl 2 , and Fe(NO 3 ) 3  such that the molar ratio of Ca to the sum of Fe to Mn is equal to 1 and the molar ratios of Fe and Mn to Ca range from 0 to 1 with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5 ; and the reacting step (b) comprises reacting the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5  with air at a temperature of from between about 650° C. to about 950° C. to form the complex metal oxide comprising Ca 2 FeMnO 5 . 
     
     
       18. The process of  claim 1 
 wherein the at least one water-soluble salt of A is a nitrate salt of A, and the at least one water-soluble salt of B is a nitrate salt of B; and 
 wherein the oxygen containing gas is air. 
 
     
     
       19. The process of  claim 18  wherein the carbonate precipitate comprises Ca 2 FeMn(CO 3 ) 5  and wherein the reacting step (a) comprises reacting water-soluble nitrate salts of the cations Ca(II), Mn(II), and Fe(II) with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5 . 
     
     
       20. The process of  claim 18  wherein the carbonate precipitate comprises Ca 2 FeMn(CO 3 ) 5  and wherein the reacting step (a) comprises reacting water-soluble nitrate salts of the cations Ca(II), Mn(II), and Fe(III) with 3 to 10 times the stoichiometric amount of carbonate or bicarbonate salt required to form each mole of the carbonate precipitate comprising Ca 2 FeMn(CO 3 ) 5 .